The reference design uses a digital potentiometer, TPL0102, in each channel for two different purposes: providing a variable resistance to account for BUF802 trimming in the composite loop circuit, and providing hysteresis control for the high-speed comparator, TLV3605. TPL0102 provides 100kΩ end-to-end resistance as well as non-volatile memory which stores the internal wiper settings.

Figure 2-15 TPL0102 Equivalent Circuit

The configuration used in the design shorts the W (wiper) and L (low) pins, so the effective resistance is equal to R_HW. Figure 2-15 shows how the effective resistance is calculated. For use in the composite loop circuit, the recommended value for the digital potentiometer is approximately 6.7kΩ to account for any variance in the BUF802 and the resistors. For the hysteresis, the recommended value is 56kΩ to provide 60mV of hysteresis voltage to the input of the comparator. Both values are chosen as per recommended values in the datasheets, but can easily be adjusted via I2C to fit any system requirement.